With the movement toward smaller developing units in conventional image forming apparatuses, and particularly in image forming apparatuses employing the tandem mode as in color copying machines, it has been difficult to automatically eject the developer. As such, in conventional image forming apparatuses of the tandem mode, the developer is replaced by first removing the developing unit from the main body and then rotating the coupling with the ejection opening facing downward, the coupling being rotated either manually or by rotating the developing unit outside the main body, as disclosed, for example, in Laid-Open Japanese Utility Model Publication No. 71757/1989 (Jitsukaihei 1-71757; Published on May 15, 1989).
Further, as disclosed in Japanese Laid-Open Patent Publication No. 89061/1994 (Tokukaihei 6-89061; published on Mar. 29, 1994), there has been proposed an automatic ejection technique. However, owning to the fact that an apparatus employing such an automatic ejection technique includes a large developing unit such as a large-sized high-speed machine, automatic ejection of the developer is performed by providing an ejection roller in addition to the stirring roller.
In an image forming apparatus employing the two-component development system, the developer is reused by first ejecting the finished developer from the developing unit and then replenishing the developing unit with a new developer. Here, care must be taken to strictly follow the proper procedure of replenishing the developer, or not to eject the developer before the developer is ready to be collected, because failure to do so results in contamination of the apparatus and its surroundings.